This invention relates generally to fluid sprinkling and more particularly to weather control spraying. The invention herein disclosed is an improvement over my U.S. Pat. No. 3,706,414 dated Dec. 19, 1972.
Numerous systems have been developed for artificially producing snow wherein water and air under pressure are in some manner mixed and commingled. The principle involved is to reduce the size of water particles to the barest minimum possible, albeit by injection of compressed air directly or indirectly with the water or mixing with air using deflectors and baffles within a mixing chamber.
Artificial snow is formed from seed crystals. These seed crystals are formed from the expansion of air expelled into the atmosphere around which minute water particles freeze and form snow. The air, being compressed, is at a higher temperature than normal ambient winder conditions and when expelled will expand to atmospheric pressure while reducing a great deal in temperature. Because of the pressure reduction, the high level of moisture present in the compressed air upon expansion will condense, immediately forming the seed crystals necessary for snow. These seed crystals are immediately formed because of the extremely low temperature condition obtained through the expansion of the air together with freezing atmospheric conditions of winter, that is, temperatures below 32.degree. F. The seed crystal thus formed can be combined with atomized water in a manner to form more snow.
In connection with the atomizing of water, the water particle size should be as small as possible, because if they are too large, depending on ambient weather conditions and the ratio of water to air mixture, they will produce ice or sleet particles which are unsatisfactory for desirable skiing conditions. Also, the greater the water pressure at the discharge nozzle, the smaller the water particles or moisture droplets upon nozzle discharge.
Examples of the jet pump principle in air and water mixing devices for producing artificial snow are shown in U.S. Pat. Nos. 3,464,625 and 3,494,559, wherein a water-air nozzle is provided so that the compressed air is introduced in an area immediately behind a centrally located water jet nozzle. The sheath of air around the water jet causes atomization of the water as it expands from the nozzle into the atmosphere.
Other types of snow making apparatus provide for the water and compressed air to be mixed together in a chamber prior to discharge from the nozzle into the atmosphere. Baffles or deflectors may be employed to aid in the mixing process in order to atomize and reduce the water into small, minute particles of water acceptable for seed crystal formation upon discharge from the nozzle. Examples of these are found in U.S. Pat. Nos. 3,010,660; 3,298,612 and 3,301,485, as well as my own U.S. Pat. No. 3,706,414. The commingling of compressed air and water in the manner taught in these patents for the most part has been the most successful means for producing artifical snow. In particular, U.S. Pat. No. 3,706,414 provides for a snow making system utilizing high snow towers having discharge nozzles at the top of the tower. Pressurized air and water are introduced at the bottom of each tower of the system where they are commingled to reduce the water into fine water particles which are discharged from the top of the tower approximately 35 feet above the ground and produce the seed crystals necessary to produce snow. The advantage obtained from this system is that due to the tower height, a characteristically long dwell time can be obtained, that is, the time between the time the seed crystals are formed upon discharge and the time the snow crystals, as formed from the seed crystals, finally settle upon the ground. This lengthy dwell time provides for sure and sufficient seed crystal formation of the atomized discharge as well as complete formation of good snow crystals upon settling to the ground. Also, this system of high snow towers does not interfere with recreational use of the ski slope, as skiers can use the slope while the snow making process is in progress. Further, a larger area of snow coverage can be effectively obtained.
Another advantage is costs, in that once this system is installed, no further costs will be incurred as the life of the system is as long as the life of the pipe employed in the system. Further, other systems require that portable snow making units be moved about the ski slope, such as shown in U.S. Pat. Nos. 3,298,612 and 3,010,660, which requires additional personnel and sometimes the aid of vehicular means to move these units from one location to another. During this procedure, it is quite difficult to have skiers continue to use the slope.
However, there are still certain disadvantages in this system as well as other systems mentioned in the area of controlling the air and water output on a continuous basis in obtaining the optimum air to water ratio. As ambient weather conditions change, particularly temperature and humidity, the proportional ratio of air and water will change. An operator can be employed to go from snow tower to snow tower making adjustments to the air to water ratio by operating the respective valves in the air and water lines to the tower to control the volume of air and water being mixed and commingled. However, the operator has no means by which to determine if he has obtained an optimum air to water ratio. As a consequence, the operator usually adds more water or air to be commingled in the tower. In many cases, ice or sleet-like particles may be formed even though the operator has attempted to obtain a desired ratio condition on a trial and error basis.
The attempt to obtain an optimum air to water ratio is further frustrated by pressure balancing. If the air and water entering the lower end of the tower are not at the same pressure, then the fluid medium having the higher pressure value will enter into the conduit or line of the lower pressure fluid medium. For example, assume that the minimum water pressure needed at ground level of the snow tower which is at the highest point on the mountain is 100 lbs. If the air compressor utilized as a capacity of 100 lbs. pressure, one must maintain 100 lbs. water pressure at the highest tower on the slope, assuming no frictional losses, to insure proper pressure balancing between water and air pressure. Actual tests have shown, however, that the maximum effective air pressure discharge from this highest tower at the tower nozzle 35 feet above the ground is approximately 70 lbs., and at its ground level is 95 lbs. The water pressure at the discharge nozzle should also be 70 lbs. Actual testing has shown that with 70 lbs. water pressure at the tower nozzle, there was an 85 lb. water pressure at the bottom of the highest tower. Thus, we are faced with a 30 lb. efficiency loss in air pressure and a 15 lb. efficiency loss in water pressure where the system pumping equipment is capable of respectively producing 100 lbs. pressure of water and air pressure.
In the above-mentioned testing, the snow making system employed is installed upon a ski slope having a 400 ft. vertical drop. By calculation, it has been found that in view of the fact that the water supplied is pumped from a water source from the top of the ski slope, the actual water pressure provided to the lower snow making tower at the bottom of the slope is approximately 172 additional pounds, rather than just 100 lbs., so that the total water pressure at this lowest tower is approximately 272 lbs. Since the maximum air pressure obtainable at the tower nozzle is 70 lbs., it is quite obvious that this additional 172 pounds of water pressure is lost and of no use because it is not needed when pressure balancing the air and water supplied to this snow tower.
From all of the foregoing, it can be readily seen that with a plurality of snow towers positioned up and down a ski slope adjacent to a ski trail, by necessity, due to differences in air and water pressures and volumes, one must attempt to regulate each tower to balance air and water pressure while also attempting to obtain optimum air to water ratios for each tower. This is practically next to impossible, because the adjustment of pressure and volume of one fluid medium seems to always cause the necessity of adjustment of the other fluid medium. Further, since the pressure value of the water differs from tower to tower all the way up the slope, the adjustment of the pressure of the entire system is limited by the tower having the lowest pressure point of water, so that the full capacity of water and air pressure that can be developed in the system cannot be efficiently utilized.
There is no question that the most expensive component is any practical snow making system is the cost of the compressed air, which represents about 90 percent of the costs of consummables in the making of snow. In particular, compressor equipment necessary for an entire ski slope is very expensive to purchase, and is usually obtained on a rental basis. Even in the face of these air compressor costs, it can be readily seen from the foregoing that these costs are further augmented by the efficiency loss of air pressure delivered to the system and discharged at the snow tower nozzles.
If these efficiency losses could be reduced in combination with a reduction of the amount of air pressure needed at the discharge nozzle, cost and operational expense of compressor and pump equipment can be substantially reduced while utilizing the pumping equipment of the snow making system at optimum efficiency levels. Air compressor costs cannot be eliminated, as compressed air is needed because of the ability of air upon expansion to provide for seed crystals. But these costs can at least be reduced through the optimum employment of equipment and the reduction of compressed air needed in snow making.
Another disadvantage in prior art snow making devices and systems is air line freeze-up. Compressed air contains considerable moisture and where freezing ambient conditions exist, the air line, particularly above the surface and at the point of conduit connection to the snow tower mixing chamber, will often freeze-up, where ambient temperatures are 20.degree. F or less. The moisture in the compressed air at this point in the conduit of the system will freeze into ice and over a period of time will freeze to a point where the conduit cross section will be completely closed off due to ice formation preventing the compressed air from reaching the tower mixing chamber. As an example, under operating conditions presently existing at Seven Springs, the water temperature entering the bottom of the snow tower is approximately 39.degree. F, and the air temperature is approximately 80.degree. F. However, the 80.degree. F air temperature will reduce below freezing relatively quickly when the compressed air is traveling through the conduit exposed to the freezing ambient atmosphere and expanding into the mixing chamber in the snow tower as compared to the water at 39.degree. F entering the same mixing chamber. It is this principle itself that quickly cools the water through the vertical length of the snow tower which is being continuously broken down or atomized by the compressed air.
This problem has also plagued the snow making devices of the past. For example, U.S. Pat. No. 3,298,612 employs a metal jacket around the mixing chamber which is not effective, particularly at lower sub-freezing tmperatures and in particular does not solve the problem of air line freeze-up in the conduit leading to the snow making device.
Also, the bleeder line shown in this patent will freeze up due to the moisture in the compressed air dissipating out due to surrounding freezing temperatures. Further, due to the nozzle configuration outside the snow making device, snow and ice will build up to a point necessitating manual removal.
This particular problem was eliminated by my U.S. Pat. No. 3,706,414. In that system, I have eliminated this problem by having very short air lines between the bottom of the snow making apparatus and the air supply lines below the ground freeze line. These short air lines exposed to the freezing atmospheric conditions are usually no more than 5 feet in length, making it impossible to cool the compressed air within these lines from the temperature of 85.degree. to 32.degree. F.
This same problem may be eliminated in other systems by having an operator reverse these lines on the average of at least once an hour to eliminate possible freeze-up in the air line. The elimination of such operational functions, such as air and water line reversing at each tower and checking and adjusting the air to water ratio at each tower would further eliminate operational costs in the snow making system.